Cross Docker network communication with Aspire

My workplace has a docker-compose file with its own network and dozens of services. It represents the fundamental behaviour of our distributed application, and I can't change it.

I wanted to experiment with Aspire at work to host our team's infrastructure and I wondered if it was possible for them to communicate in the way I needed.

In short, it is.

This prototype demonstrates how an Aspire run service, or Docker container, can hit a Docker container run in parallel with docker-compose.

Diagram

Step 1: The consumer hits the web project ColinCCook.AspireRunService

Step 1a: The consumer can either call /direct-request, which is intended for the web project to try to call http://barservice.colin directly.

Step 1b: Or it can call /via-container, which calls a mockservice container for it to proxy to http://barservice.colin instead.

Step 2: Resolving http://barservice.colin

The hosts file of the development environment points http://barservice.com to itself.

Step 3: NGINX proxies calls to http://barservice.com to a another mockserver container

This NGINX container has been run via the docker-compose.yaml file, and shares a network with another mockserver container.

Step 4: MockServer returns a Created/201 or Accepted/202, depending on the url.

If called with /foo it returns a 201 (if the web service hit it directly).

If called with /bar it returns a 202 (via the proxy container in Aspire)

Running the prototype yourself

There are integration tests that confirm that Created/201 and Accepted/202 are correctly returned by the web service.

In order for them to be run successfully, or to run Aspire yourself, follow these steps:

• Make sure your hosts file is set up to route requests for barservice.colin, see below for instructions
• Docker compose up the /docker-compose/docker-compose.yaml file
• Run the Aspire orchestration ColinCCook.AppHost.AppHost, or, build and run the unit tests.

Setting hosts file macOS

1. Open Terminal

2. Edit the hosts file using nano (recommended for beginners):

   sudo nano /etc/hosts

3. Add this line at the end of the file:

   127.0.0.1    barservice.colin
   

4. Save and exit:

   • Press Ctrl+X, then Y, then Enter

5. Flush DNS cache:

   sudo dscacheutil -flushcache
   sudo killall -HUP mDNSResponder

6. Verify the entry was added. It should output the line you've just added:

   cat /etc/hosts | grep barservice.colin

Setting hosts file Windows

1. Open Command Prompt as Administrator:

   • Press Win + X and select "Command Prompt (Admin)" or "Windows PowerShell (Admin)"
   • Or search for "cmd" in Start menu, right-click and select "Run as administrator"

2. Edit the hosts file using notepad:

   notepad C:\Windows\System32\drivers\etc\hosts

3. Add this line at the end of the file:

   127.0.0.1    barservice.colin
   

4. Save and exit:

   • Press Ctrl+S to save
   • Close Notepad

5. Flush DNS cache:

   ipconfig /flushdns

6. Verify the entry was added:

   findstr "barservice.colin" C:\Windows\System32\drivers\etc\hosts